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developed and reaches beyond the median coxre. . The legs are long 
and more slender than in the female. The tail is small and knob- 
like, and bears two small bristles; the last segment is rounded and 
provided with four smali bristles. The mature male is extremely 
active and restless and is continually running about in search of 
mature females. Copulation lasts but a short time. 
HAMAMELISTES SPINOSUS Shimer. 
Hamamelistes spinosus Shimer, Trans. Amer. Ent. Soc., vol. 1, p. 284, 1867. 
Hormaphis spinosus, Bull. U. 8S. Geol. Geog. Surv. Terr., Vol. V, No. 1, 
p. 14, 1879. 
Hormaphis papyracee Oestlund, Geol. and Nat. Hist. Surv. of Minn. 
Bull. 4, Synopsis of Aphid of Minn., p. 13, 1887. 
The life history of the second species of gall-making Aphids, inhab- 
iting both the witch-hazel and birch, is as remarkable and interesting 
as that of Hormaphis hamamelidis. Its earlier generations, asin the 
former species, subsist upon the witch-hazel, but instead of infesting 
the leaves select the young and dormant flower buds for their future 
operations, which gradually are changed into conspicuous, spiny galls, 
the architects of which, at the proper time, forsake also their old 
home and migrate to the birches to consign to them their progeny in 
order to complete the cycle of existence of the species, but, unlike 
Hi. hamamelidis, which completes its cycle within the space of one 
year, this species hibernates on the birch, on which, during the fol- 
lowing spring, it produces two additional generations, the second one 
of which returns during June to the witch-hazel for the purpose of 
producing the sexed generation. These return migrants appear just 
about the time that the spring migrants of H. hamamelidis leave 
their galls, so that during this cross migration both species may 
frequently be found simultaneously upon both plants, which oceur- 
rence during my earlier observations caused considerable confusion 
and speculation whether these two forms were only variations of one 
or whether there were really two distinct species. Continued studies, 
however, have clearly demonstrated that these two forms, notwith- 
standing their great similarity in venation and general appearance, 
are good species, belonging to two distinet genera. 
The genus Hamamelistes was described by Dr. H. Shimer, of Mount 
Carmel, Ill., in the Transactions of the American Entomological 
Society, vol. 1, page 284, 1867, to include two gail making species 
found on the witch-hazel, without, however, being aware that the 
first one of these two species, to which he gave the name of Hama- 
melistes cornu, had previously been described by Dr. A. Fitch under 
the name of Byrsocrypta hamamelidis, for which subsequently Baron 
Osten Sacken erected the genus Hormaphis. Since, however, the 
antennal characters of spinosus are markedly different from those of 
